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const expect = @import("std").testing.expect;
const mem = @import("std").mem;
// array literal
const message = [_]u8{ 'h', 'e', 'l', 'l', 'o' };
// get the size of an array
comptime {
expect(message.len == 5);
}
// A string literal is a pointer to an array literal.
const same_message = "hello";
comptime {
expect(mem.eql(u8, &message, same_message));
}
test "iterate over an array" {
var sum: usize = 0;
for (message) |byte|
sum += byte;
expect(sum == 'h' + 'e' + 'l' * 2 + 'o');
}
// modifiable array
var some_integers: [100]i32 = undefined;
test "modify an array" {
for (some_integers) |*item, i|
item.* = @intCast(i32, i);
expect(some_integers[10] == 10);
expect(some_integers[99] == 99);
}
// array concatenation works if the values are known
// at compile time
const part_one = [_]i32{ 1, 2, 3, 4 };
const part_two = [_]i32{ 5, 6, 7, 8 };
const all_of_it = part_one ++ part_two;
comptime {
expect(mem.eql(i32, &all_of_it, &[_]i32{ 1, 2, 3, 4, 5, 6, 7, 8 }));
}
// remember that string literals are arrays
const hello = "hello";
const world = "world";
const hello_world = hello ++ " " ++ world;
comptime {
expect(mem.eql(u8, hello_world, "hello world"));
}
// ** does repeating patterns
const pattern = "ab" ** 3;
comptime {
expect(mem.eql(u8, pattern, "ababab"));
}
// initialize an array to zero
const all_zero = [_]u16{0} ** 10;
comptime {
expect(all_zero.len == 10);
expect(all_zero[5] == 0);
}
// use compile-time code to initialize an array
var fancy_array = init: {
var initial_value: [10]Point = undefined;
for (initial_value) |*pt, i| {
pt.* = Point{
.x = @intCast(i32, i),
.y = @intCast(i32, i) * 2,
};
}
break :init initial_value;
};
const Point = struct {
x: i32,
y: i32,
};
test "compile-time array initialization" {
expect(fancy_array[4].x == 4);
expect(fancy_array[4].y == 8);
}
// call a function to initialize an array
var more_points = [_]Point{makePoint(3)} ** 10;
fn makePoint(x: i32) Point {
return Point{
.x = x,
.y = x * 2,
};
}
test "array initialization with function calls" {
expect(more_points[4].x == 3);
expect(more_points[4].y == 6);
expect(more_points.len == 10);
}
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